// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2020 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef BITCOIN_WALLET_DB_H
#define BITCOIN_WALLET_DB_H

#include <clientversion.h>
#include <fs.h>
#include <streams.h>
#include <support/allocators/secure.h>
#include <util/memory.h>

#include <atomic>
#include <memory>
#include <string>

struct bilingual_str;

void SplitWalletPath(const fs::path& wallet_path, fs::path& env_directory, std::string& database_filename);

/** RAII class that provides access to a WalletDatabase */
class DatabaseBatch
{
private:
    virtual bool ReadKey(CDataStream&& key, CDataStream& value) = 0;
    virtual bool WriteKey(CDataStream&& key, CDataStream&& value, bool overwrite=true) = 0;
    virtual bool EraseKey(CDataStream&& key) = 0;
    virtual bool HasKey(CDataStream&& key) = 0;

public:
    explicit DatabaseBatch() {}
    virtual ~DatabaseBatch() {}

    DatabaseBatch(const DatabaseBatch&) = delete;
    DatabaseBatch& operator=(const DatabaseBatch&) = delete;

    virtual void Flush() = 0;
    virtual void Close() = 0;

    template <typename K, typename T>
    bool Read(const K& key, T& value)
    {
        CDataStream ssKey(SER_DISK, CLIENT_VERSION);
        ssKey.reserve(1000);
        ssKey << key;

        CDataStream ssValue(SER_DISK, CLIENT_VERSION);
        if (!ReadKey(std::move(ssKey), ssValue)) return false;
        try {
            ssValue >> value;
            return true;
        } catch (const std::exception&) {
            return false;
        }
    }

    template <typename K, typename T>
    bool Write(const K& key, const T& value, bool fOverwrite = true)
    {
        CDataStream ssKey(SER_DISK, CLIENT_VERSION);
        ssKey.reserve(1000);
        ssKey << key;

        CDataStream ssValue(SER_DISK, CLIENT_VERSION);
        ssValue.reserve(10000);
        ssValue << value;

        return WriteKey(std::move(ssKey), std::move(ssValue), fOverwrite);
    }

    template <typename K>
    bool Erase(const K& key)
    {
        CDataStream ssKey(SER_DISK, CLIENT_VERSION);
        ssKey.reserve(1000);
        ssKey << key;

        return EraseKey(std::move(ssKey));
    }

    template <typename K>
    bool Exists(const K& key)
    {
        CDataStream ssKey(SER_DISK, CLIENT_VERSION);
        ssKey.reserve(1000);
        ssKey << key;

        return HasKey(std::move(ssKey));
    }

    virtual bool StartCursor() = 0;
    virtual bool ReadAtCursor(CDataStream& ssKey, CDataStream& ssValue, bool& complete) = 0;
    virtual void CloseCursor() = 0;
    virtual bool TxnBegin() = 0;
    virtual bool TxnCommit() = 0;
    virtual bool TxnAbort() = 0;
};

/** An instance of this class represents one database.
 **/
class WalletDatabase
{
public:
    /** Create dummy DB handle */
    WalletDatabase() : nUpdateCounter(0), nLastSeen(0), nLastFlushed(0), nLastWalletUpdate(0) {}
    virtual ~WalletDatabase() {};

    /** Open the database if it is not already opened. */
    virtual void Open(const char* mode) = 0;

    //! Counts the number of active database users to be sure that the database is not closed while someone is using it
    std::atomic<int> m_refcount{0};
    /** Indicate the a new database user has began using the database. Increments m_refcount */
    virtual void AddRef() = 0;
    /** Indicate that database user has stopped using the database and that it could be flushed or closed. Decrement m_refcount */
    virtual void RemoveRef() = 0;

    /** Rewrite the entire database on disk, with the exception of key pszSkip if non-zero
     */
    virtual bool Rewrite(const char* pszSkip=nullptr) = 0;

    /** Back up the entire database to a file.
     */
    virtual bool Backup(const std::string& strDest) const = 0;

    /** Make sure all changes are flushed to database file.
     */
    virtual void Flush() = 0;
    /** Flush to the database file and close the database.
     *  Also close the environment if no other databases are open in it.
     */
    virtual void Close() = 0;
    /* flush the wallet passively (TRY_LOCK)
       ideal to be called periodically */
    virtual bool PeriodicFlush() = 0;

    virtual void IncrementUpdateCounter() = 0;

    virtual void ReloadDbEnv() = 0;

    /** Return path to main database file for logs and error messages. */
    virtual std::string Filename() = 0;

    std::atomic<unsigned int> nUpdateCounter;
    unsigned int nLastSeen;
    unsigned int nLastFlushed;
    int64_t nLastWalletUpdate;

    /** Make a DatabaseBatch connected to this database */
    virtual std::unique_ptr<DatabaseBatch> MakeBatch(const char* mode = "r+", bool flush_on_close = true) = 0;
};

/** RAII class that provides access to a DummyDatabase. Never fails. */
class DummyBatch : public DatabaseBatch
{
private:
    bool ReadKey(CDataStream&& key, CDataStream& value) override { return true; }
    bool WriteKey(CDataStream&& key, CDataStream&& value, bool overwrite=true) override { return true; }
    bool EraseKey(CDataStream&& key) override { return true; }
    bool HasKey(CDataStream&& key) override { return true; }

public:
    void Flush() override {}
    void Close() override {}

    bool StartCursor() override { return true; }
    bool ReadAtCursor(CDataStream& ssKey, CDataStream& ssValue, bool& complete) override { return true; }
    void CloseCursor() override {}
    bool TxnBegin() override { return true; }
    bool TxnCommit() override { return true; }
    bool TxnAbort() override { return true; }
};

/** A dummy WalletDatabase that does nothing and never fails. Only used by unit tests.
 **/
class DummyDatabase : public WalletDatabase
{
public:
    void Open(const char* mode) override {};
    void AddRef() override {}
    void RemoveRef() override {}
    bool Rewrite(const char* pszSkip=nullptr) override { return true; }
    bool Backup(const std::string& strDest) const override { return true; }
    void Close() override {}
    void Flush() override {}
    bool PeriodicFlush() override { return true; }
    void IncrementUpdateCounter() override { ++nUpdateCounter; }
    void ReloadDbEnv() override {}
    std::string Filename() override { return "dummy"; }
    std::unique_ptr<DatabaseBatch> MakeBatch(const char* mode = "r+", bool flush_on_close = true) override { return MakeUnique<DummyBatch>(); }
};

enum class DatabaseFormat {
    BERKELEY,
};

struct DatabaseOptions {
    bool require_existing = false;
    bool require_create = false;
    uint64_t create_flags = 0;
    SecureString create_passphrase;
    bool verify = true;
};

enum class DatabaseStatus {
    SUCCESS,
    FAILED_BAD_PATH,
    FAILED_BAD_FORMAT,
    FAILED_ALREADY_LOADED,
    FAILED_ALREADY_EXISTS,
    FAILED_NOT_FOUND,
    FAILED_CREATE,
    FAILED_LOAD,
    FAILED_VERIFY,
    FAILED_ENCRYPT,
};

std::unique_ptr<WalletDatabase> MakeDatabase(const fs::path& path, const DatabaseOptions& options, DatabaseStatus& status, bilingual_str& error);

#endif // BITCOIN_WALLET_DB_H
